On Mon, 2017-08-14 at 22:49 +1000, Michael Ellerman wrote:

Nicholas Piggin [off-list ref] writes:

quoted

This removes the RMA limit on powernv platform, which constrains
early allocations such as PACAs and stacks. There are still other
restrictions that must be followed, such as bolted SLB limits, but
real mode addressing has no constraints.

For radix, should we consider making the PACAs chip/node local ?

quoted

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/mm/hash_utils_64.c | 24 +++++++++++++++---------
 arch/powerpc/mm/pgtable-radix.c | 33 +++++++++++++++++----------------

I missed that we'd duplicated this logic for radix vs hash [yes I know I
merged the commit that did it :)]

quoted

diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c
index 671a45d86c18..61ca17d81737 100644
--- a/arch/powerpc/mm/pgtable-radix.c
+++ b/arch/powerpc/mm/pgtable-radix.c

@@ -598,22 +598,23 @@ void radix__setup_initial_memory_limit(phys_addr_t first_memblock_base,
 	 * physical on those processors
 	 */
 	BUG_ON(first_memblock_base != 0);
-	/*
-	 * We limit the allocation that depend on ppc64_rma_size
-	 * to first_memblock_size. We also clamp it to 1GB to
-	 * avoid some funky things such as RTAS bugs.

That comment about RTAS is 7 years old, and I'm pretty sure it was a
historical note when it was written.

I'm inclined to drop it and if we discover new bugs with RTAS on Power9
then we can always put it back.

quoted

-	 *
-	 * On radix config we really don't have a limitation
-	 * on real mode access. But keeping it as above works
-	 * well enough.

Ergh.

quoted

-	 */
-	ppc64_rma_size = min_t(u64, first_memblock_size, 0x40000000);
-	/*
-	 * Finally limit subsequent allocations. We really don't want
-	 * to limit the memblock allocations to rma_size. FIXME!! should
-	 * we even limit at all ?
-	 */

So I think we should just delete this function entirely.

Any objections?

cheers